TPA induces the expression of EC-SOD in human monocytic THP-1 cells: Involvement of PKC, MEK/ERK and NOX-derived ROS

Cellular RNA and DNA sensing pathways are essential for the dose-dependent response of human monocytes to ionizing radiation

Circulating monocytes are important players of the inflammatory response to ionizing radiation (IR). These IR-resistant immune cells migrate to radiation-damaged tissues and differentiate into macrophages that phagocytize dying cells, but also facilitate inflammation. Besides the effect of damage-associated molecular patterns, released from irradiated tissues, the inflammatory activation of monocytes and macrophages is largely dependent on IR-induced DNA damage and aberrant transcriptional activity, which may facilitate expression of type I interferons (IFN-I) and numerous inflammation-related genes. We analyzed the accumulation of dsRNA, dsDNA fragments, and RNA:DNA hybrids in the context of induction of RNA-triggered MAVS-mediated and DNA-triggered STING-mediated signaling pathways, in primary human monocytes and a monocytic cell line, THP1, in response to various doses of gamma IR. We found that exposure to lower doses (<7.5 Gy) led to the accumulation of dsRNA, along with dsDNA and RNA:DNA hybrids and activated both MAVS and STING pathway-induced gene expression and signaling activity of IFN-I. Higher doses of IR resulted in the reduced dsRNA level, degradation of RNA-sensing mediators involved in MAVS signaling and coincided with an increased accumulation of dsDNA and RNA:DNA hybrids that correlated with elevated STING signaling and NF-κB-dependent gene expression. While both pathways activate IFN-I expression, using MAVS- and STING-knockout THP1 cells, we identified differences in the spectra of interferon-stimulated genes (ISGs) that are associated with each specific signaling pathway and outlined a large group of STING signaling-associated genes. Using the RNAi technique, we found that increasing the dose of IR activates STING signaling through the DNA sensor cGAS, along with suppression of the DDX41 helicase, which is known to reduce the accumulation of RNA:DNA hybrids and thereby limit cGAS/STING signaling activity. Together, these results indicate that depending on the applied dose, IR leads to the activation of either dsRNA-induced MAVS signaling, which predominantly leads to the expression of both pro- and anti-inflammatory markers, or dsDNA-induced STING signaling that contributes to pro-inflammatory activation of the cells. While RNA:DNA hybrids boost both MAVS- and STING-mediated signaling pathways, these structures being accumulated upon high IR doses promote type I interferon expression and appear to be potent enhancers of radiation dose-dependent pro-inflammatory activation of monocytes.

Curcumin, inflammation, and neurological disorders: How are they linked?

Background

Despite the extensive research in recent years, the current treatment modalities for neurological disorders are suboptimal. Curcumin, a polyphenol found in Curcuma genus, has been shown to mitigate the pathophysiology and clinical sequalae involved in neuroinflammation and neurodegenerative diseases.

Methods

We searched PubMed database for relevant publications on curcumin and its uses in treating neurological diseases. We also reviewed relevant clinical trials which appeared on searching PubMed database using 'Curcumin and clinical trials'.

Results

This review details the pleiotropic immunomodulatory functions and neuroprotective properties of curcumin, its derivatives and formulations in various preclinical and clinical investigations. The effects of curcumin on neurodegenerative diseases such as Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), brain tumors, epilepsy, Huntington's disorder (HD), ischemia, Parkinson's disease (PD), multiple sclerosis (MS), and traumatic brain injury (TBI) with a major focus on associated signalling pathways have been thoroughly discussed.

Conclusion

This review demonstrates curcumin can suppress spinal neuroinflammation by modulating diverse astroglia mediated cascades, ensuring the treatment of neurological disorders.

Alpha fetoprotein promotes polarization of macrophages towards M2-like phenotype and inhibits macrophages to phagocytize hepatoma cells

Alpha-fetoprotein(AFP) is a cancer biomarker for the diagnosis of hepatocellular carcinoma(HCC); however, its role in macrophage polarization and phagocytosis remains unclear. In the present study, we explored the correlation between AFP regulation of macrophage function and the possible regulatory mechanisms. Human mononuclear leukemia cells (THP-1) and monocytes from healthy donors were used to analyze the effect of AFP on the macrophages' phenotype and phagocytosis. THP-1 cells and healthy human donor-derived monocytes were polarized into M0 macrophages induced by phorbol ester (PMA), and M0 macrophages were polarized into M1 macrophages induced by lipopolysaccharide(LPS) and interferon-γ(IFN-γ). Interleukin-4(IL-4) and interleukin-13(IL-13) were used to induce M0 macrophage polarization into M2 macrophages. Tumor-derived AFP(tAFP) stimulated M0 macrophage polarization into M2 macrophages and inhibited M1 macrophages to phagocytize HCC cells. The role of AFP in promoting macrophage polarization into M2 macrophages and inhibiting the M1 macrophages to phagocytize HCC cells may be involved in activating the PI3K/Akt signaling pathway. AFP could also enhanced the migration ability of macrophages and inhibited the apoptosis of HCC cells when co-cultured with M1-like macrophages. AFP is a pivotal cytokine that inhibits macrophages to phagocytize HCC cells.

Extracellular-superoxide dismutase DNA methylation promotes oxidative stress in homocysteine-induced atherosclerosis

In the present study, we investigate the effect of homocysteine (Hcy) on extracellular-superoxide dismutase (EC-SOD) DNA methylation in the aorta of mice, and explore the underlying mechanism in macrophages, trying to identify the key targets of Hcy-induced EC-SOD methylation changes. ApoE ^-/- mice are fed different diets for 15 weeks, EC-SOD and DNA methyltransferase 1 (DNMT1) expression levels are detected by RT-PCR and western blot analysis. EC-SOD methylation levels are assessed by ntMS-PCR. After EC-SOD overexpression or knockdown in macrophages, following the transfection of macrophages with pEGFP-N1-DNMT1, the methylation levels of EC-SOD are detected. Our data show that the concentrations of Hcy and the area of atherogenic lesions are significantly increased in ApoE ^-/- mice fed with a high-methionine diet, and have a positive correlation with the levels of superoxide anions, which indicates that Hcy-activated superoxide anions enhance the development of atherogenic lesions. EC-SOD expression is suppressed by Hcy, and the content of superoxide anion is increased when EC-SOD is silenced by RNAi in macrophages, suggesting that EC-SOD plays a major part in oxidative stress induced by Hcy. Furthermore, the promoter activity of EC-SOD is increased following transfection with the -1/-1100 fragment, and EC-SOD methylation level is significantly suppressed by Hcy, and more significantly decreased upon DNMT1 overexpression. In conclusion, Hcy may alter the DNA methylation status and DNMT1 acts as the essential enzyme in the methyl transfer process to disturb the status of EC-SOD DNA methylation, leading to decreased expression of EC-SOD and increased oxidative stress and atherosclerosis.

Inhibitory effects of 4-hydroperoxy-2-decenoic acid ethyl ester on phorbol ester- and TGF-β1-induced MMPs expression

Matrix metalloproteinases (MMPs), zinc-containing proteinases, play a critical role in tumour progression by degrading extracellular matrix components. MMP2 and MMP9 are secreted from tumour-associated macrophages as well as tumour cells and have been implicated in the formation of the tumour microenvironment. Therefore, the inhibition of these MMPs may suppress tumour progression and metastasis. 4-Hydroperoxy-2-decenoic acid ethyl ester (HPO-DAEE) is known to cause apoptosis in the human lung cancer cell line A549 by inducing endoplasmic reticulum (ER) stress. However, the effects of HPO-DAEE on tumour progression remain unclear. HPO-DAEE pre-treatment significantly suppressed phorbol 12-myristate 13-acetate (TPA)-triggered MMP activation in human monocytic THP-1 cells. It also enhanced the expression of haem oxygenase-1, an antioxidant enzyme, and suppressed the TPA-triggered intracellular accumulation of reactive oxygen species (ROS). Furthermore, HPO-DAEE suppressed transforming growth factor-β1-triggered human prostate cancer PC3 cell migration and this was accompanied by the inhibition of MMP expression and activities. The present results indicate that HPO-DAEE may exert inhibitory effects on tumour progression by suppressing MMP expression and activities.

[Regulation of Extracellular Redox Homeostasis in Tumor Microenvironment]

Excessive generation of reactive oxygen species (ROS) has been implicated in the progression of tumors. Superoxide dismutase 3 (SOD3) is a copper-containing secretory antioxidative enzyme that plays a critical role in redox homeostasis, particularly in extracellular spaces. Considerable evidence suggests that SOD3 protein expression is significantly decreased or lost in several tumor tissues, and this loss results in tumor metastasis. On the other hand, epigenetic disturbances, including DNA hyper-/hypomethylation, histone de/acetylation, and histone de/methylation, may be involved in tumorigenesis and the progression of metastasis. However, regulation of SOD3 in the tumor microenvironment and the involvement of epigenetics in its expression remain unclear. To elucidate the molecular mechanisms underlying SOD3 expression, we investigated the involvement of epigenetics, including DNA methylation and histone modifications, in its regulation in tumor cells and macrophages. SOD3 expression in human monocytic THP-1 cells and human lung cancer A549 cells was silenced by DNA hypermethylation within the SOD3 promoter region. Furthermore, the DNA demethylase, ten-eleven translocation 1, was shown for the first time to play a key role in regulation of DNA methylation within that region. We also demonstrated that myocyte enhancer factor 2 functioned as one of the transcription factors of SOD3 expression in THP-1 cells. Collectively, these novel results will contribute to the elucidation of epigenetic redox regulation, and may provide important insights into tumorigenesis and tumor metastasis.

Inhibitory mechanism of ginsenoside Rh3 on granulocyte-macrophage colony-stimulating factor expression in UV-B-irradiated murine SP-1 keratinocytes

Background

Ultraviolet (UV) goes through the epidermis and promotes release of inflammatory cytokines in keratinocytes. Granulocyte–macrophage colony-stimulating factor (GM-CSF), one of the keratinocyte-derived cytokines, regulates proliferation and differentiation of melanocytes. Extracellular signal–regulated kinase (ERK1/2) and protein kinase C (PKC) signaling pathways regulate expression of GM-CSF. Based on these results, we found that ginsenoside Rh3 prevented GM-CSF production and release in UV-B–exposed SP-1 keratinocytes and that this inhibitory effect resulted from the reduction of PKCδ and ERK phosphorylation.

Methods

We investigated the mechanism by which ginsenoside Rh3 from Panax ginseng inhibited GM-CSF release from UV-B–irradiated keratinocytes.

Results

Treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA) or UV-B induced release of GM-CSF in the SP-1 keratinocytes. To elucidate whether the change in GM-CSF expression could be related to PKC signaling, the cells were pretreated with H7, an inhibitor of PKC, and irradiated with UV-B. GM-CSF was decreased by H7 in a dose-dependent manner. When we analyzed which ginsenosides repressed GM-CSF expression among 15 ginsenosides, ginsenoside Rh3 showed the largest decline to 40% of GM-CSF expression in enzyme-linked immunosorbent assay. Western blot analysis showed that TPA enhanced the phosphorylation of PKCδ and ERK in the keratinocytes. When we examined the effect of ginsenoside Rh3, we identified that ginsenoside Rh3 inhibited the TPA-induced phosphorylation levels of PKCδ and ERK.

Conclusion

In summary, we found that ginsenoside Rh3 impeded UV-B–induced GM-CSF production through repression of PKCδ and ERK phosphorylation in SP-1 keratinocytes.

Induction of Human-Lung-Cancer-A549-Cell Apoptosis by 4-Hydroperoxy-2-decenoic Acid Ethyl Ester through Intracellular ROS Accumulation and the Induction of Proapoptotic CHOP Expression

Royal jelly, a natural product secreted by honeybees, contains several fatty acids, such as 10-hydroxy-2-decenoic acid (DE), and shows anti- and pro-apoptotic properties. 4-Hydroperoxy-2-decenoic acid ethyl ester (HPO-DAEE), a DE derivative, exhibits potent antioxidative activity; however, it currently remains unclear whether HPO-DAEE induces cancer-cell death. In the present study, treatment with HPO-DAEE induced human-lung-cancer-A549-cell death (52.7 ± 10.2%) that was accompanied by DNA fragmentation. Moreover, the accumulation of intracellular reactive oxygen species (ROS, 2.38 ± 0.1-fold) and the induction of proapoptotic CCAAT-enhancer-binding-protein-homologous-protein (CHOP) expression (18.4 ± 4.0-fold) were observed in HPO-DAEE-treated cells. HPO-DAEE-elicited CHOP expression and cell death were markedly suppressed by pretreatment with N-acetylcysteine (NAC), an antioxidant, by 2.40 ± 1.57-fold and 5.7 ± 1.6%, respectively. Pretreatment with 4-phenylbutyric acid (PBA), an inhibitor of endoplasmic reticulum stress, also suppressed A549-cell death (38.4 ± 1.1%). Furthermore, we demonstrated the involvement of extracellular-signal-regulated protein kinase (ERK) and p38-related signaling in HPO-DAEE-elicited cell-death events. Overall, we concluded that HPO-DAEE induces A549-cell apoptosis through the ROS-ERK-p38 pathway and, at least in part, the CHOP pathway.

Liquiritin suppresses UVB‑induced skin injury through prevention of inflammation, oxidative stress and apoptosis through the TLR4/MyD88/NF‑κB and MAPK/caspase signaling pathways

Solar ultraviolet B (UVB) radiation is known to trigger inflammation, oxidative stress and apoptotic responses through various signaling pathways, which eventually lead to skin cancer. The present study investigated whether liquiritin suppresses UVB-induced skin injury in viv and in vitr using SKH-1 hairless mice and HACAT cells, respectively. The animals were exposed to UVB irradiation (180 mJ/cm²) for 20 min, followed by liquiritin treatment. The findings indicated that UVB exposure resulted in the excessive release of pro-inflammatory cytokines, including interleukin (IL)-1β, tumor necrosis factor (TNF)-α, IL-18, IL-6 and cyclooxygenase (COX)2, which were dependent on the toll-like receptor (TLR)4/myeloid differentiation factor 88 (MyD88)/nuclear factor-κB (NF-κB) signaling pathway. Oxidative stress was also observed, evidenced by reduced antioxidants and elevated oxidants. Apoptosis, examined using terminal deoxynucleotidyl transferase dUTP nick end labeling and crystal violet staining, suggested that UVB irradiation caused cell death in viv and in vitro, which was closely associated with p38/c-Jun N-terminal kinase and caspase activity. Of note, liquiritin treatment in mice and cells exposed to UVB showed reduced inflammatory response, oxidative stress and apoptosis through inhibiting the activation of TLR4/MyD88/NF-κB mitogen-activated protein kinases and caspase pathways, and downregulating the release of oxidants. Overall, the data revealed that liquiritin may be a useful compound against UVB-induced skin injury.

Copper chaperone antioxidant-1, Atox-1, is involved in the induction of SOD3 in THP-1 cells

Superoxide dismutase (SOD) 3, a copper (Cu)-containing anti-oxidative enzyme, plays a key role in extracellular redox homeostasis. Cu chaperone antioxidant-1 (Atox-1) not only delivers Cu ions to SOD3 at the trans-Golgi network, it also functions as a transcription factor of SOD3; however, the role of Atox-1 in the regulation of SOD3 during the monocytic differentiation of THP-1 cells has not yet been elucidated. A treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA) induced the expression of the Cu transport protein ATP7A in THP-1 cells. On the other hand, the nuclear translocation of Atox-1 was detected in TPA-treated THP-1 cells, and was suppressed in the presence of the Cu chelator, bathocuproinedisulfonic acid. Furthermore, Atox-1 bound to the SOD3 promoter region in TPA-treated THP-1 cells. The overexpression of Atox-1 in THP-1 cells significantly enhanced TPA-elicited SOD3 expression, whereas its knockdown suppressed this induction. The present results demonstrate that Atox-1 functions as a key molecule in TPA-elicited SOD3 expression.

TLR2 activation induces antioxidant defence in human monocyte-macrophage cell line models

When monocytes are recruited to inflammation/infection sites, extravasate and differentiate into macrophages, they encounter increasing levels of oxidative stress, both from exogenous and endogenous sources. In this study, we aimed to determine whether there are specific biochemical mechanisms responsible for an increase in oxidative stress resistance in differentiating macrophages. We performed experiments on in vitro cell line models of the monocyte-macrophage differentiation axis (less differentiated THP-1 cells and more differentiated Mono Mac 6 cells). At the same time, we verified the hypothesis that activating monocyte/macrophage innate immune response by pathogens (exemplified by stimulating the TLR2 pattern recognition receptor) would further strengthen cellular antioxidant defences. We found that resistance to exogenous oxidative stress increased substantially both during differentiation and upon activation of TLR2. This increase in antioxidant resistance was accompanied by decrease in free radical damage to cellular proteins. On the molecular level, this resistance was mediated especially by increased levels and activity of glutathione, glutathione-related antioxidant enzymes and Mn superoxide dismutase, as shown by gene expression assays, Western blotting and enzyme activity assays. Moreover, upon TLR2 activation additional molecular mechanisms came into play, conferring additional resistance levels even upon differentiated macrophage-like cells, mainly related to thioredoxin-linked antioxidant enzymes.

Royal Jelly Constituents Increase the Expression of Extracellular Superoxide Dismutase through Histone Acetylation in Monocytic THP-1 Cells

Extracellular superoxide dismutase (EC-SOD) is one of the main SOD isozymes and plays an important role in the prevention of cardiovascular diseases by accelerating the dismutation reaction of superoxide. Royal jelly includes 10-hydroxy-2-decenoic acid (10H2DA, 2), which regulates the expression of various types of genes in epigenetics through the effects of histone deacetylase (HDAC) antagonism. The expression of EC-SOD was previously reported to be regulated epigenetically through histone acetylation in THP-1 cells. Therefore, we herein evaluated the effects of the royal jelly constituents 10-hydroxydecanoic acid (10HDA, 1), sebacic acid (SA, 3), and 4-hydroperoxy-2-decenoic acid ethyl ester (4-HPO-DAEE, 4), which is a derivative of 2, on the expression of EC-SOD in THP-1 cells. The treatment with 1 mM 1, 2, or 3 or 100 μM 4 increased EC-SOD expression and histone H3 and H4 acetylation levels. Moreover, the enrichment of acetylated histone H4 was observed in the proximal promoter region of EC-SOD and was caused by the partial promotion of ERK phosphorylation (only 4) and inhibition of HDAC activities, but not by the expression of HDACs. Overall, 4 exerted stronger effects than 1, 2, or 3 and has potential as a candidate or lead compound against atherosclerosis.

Caffeic acid phenethyl ester suppresses monocyte adhesion to the endothelium by inhibiting NF-κB/NOX2-derived ROS signaling

Caffeic acid phenethyl ester (CAPE), one of the major polyphenols, exhibits anti-oxidative, anti-bacterial, and anti-cancer properties. Atherosclerosis is a chronic inflammatory disease, the progression of which is closely related to the accumulated adhesion of inflammatory monocytes/macrophages to the endothelium. We herein determined whether CAPE and its derivatives suppressed THP-1 cell adhesion to human umbilical vein endothelial cells (HUVEC). Of the four polyphenols tested, CAPE significantly suppressed the 12-O-tetradecanoylphorbol 13-acetate (TPA)-elicited expression of cluster for differentiation (CD) 11b, 14, and 36, and this was accompanied by the inhibition of THP-1 cell adhesion to HUVEC. CAPE also suppressed the activation of TPA-elicited nuclear factor-κB (NF-κB) and accumulation of NADPH oxidase 2 (NOX2)-derived reactive oxygen species (ROS), but did not affect extracellular signal-regulated kinase (ERK) phosphorylation. Taken together, these results demonstrated that CAPE suppressed THP-1 cell adhesion to HUVEC through, at least in part, the NF-κB, NOX2, and ROS-derived signaling axis.

The Reactive Oxygen Species in Macrophage Polarization: Reflecting Its Dual Role in Progression and Treatment of Human Diseases

High heterogeneity of macrophage is associated with its functions in polarization to different functional phenotypes depending on environmental cues. Macrophages remain in balanced state in healthy subject and thus macrophage polarization may be crucial in determining the tissue fate. The two distinct populations, classically M1 and alternatively M2 activated, representing the opposing ends of the full activation spectrum, have been extensively studied for their associations with several disease progressions. Accumulating evidences have postulated that the redox signalling has implication in macrophage polarization and the key roles of M1 and M2 macrophages in tissue environment have provided the clue for the reasons of ROS abundance in certain phenotype. M1 macrophages majorly clearing the pathogens and ROS may be crucial for the regulation of M1 phenotype, whereas M2 macrophages resolve inflammation which favours oxidative metabolism. Therefore how ROS play its role in maintaining the homeostatic functions of macrophage and in particular macrophage polarization will be reviewed here. We also review the biology of macrophage polarization and the disturbance of M1/M2 balance in human diseases. The potential therapeutic opportunities targeting ROS will also be discussed, hoping to provide insights for development of target-specific delivery system or immunomodulatory antioxidant for the treatment of ROS-related diseases.

Suppression of EC-SOD by oxLDL During Vascular Smooth Muscle Cell Proliferation

Reactive oxygen species (ROS) produced by endothelial cells and macrophages play important roles in atherogenesis because they promote the formation of oxidized low-density lipoproteins (oxLDL). Extracellular-superoxide dismutase (EC-SOD) is mainly produced by vascular smooth muscle cells (VSMCs), is secreted into the extracellular space, and protects cells from the damaging effects of the superoxide anion. Thus, the expression of EC-SOD in VSMCs is crucial for protecting cells against atherogenesis; however, oxLDL-induced changes in the expression of EC-SOD in VSMCs have not yet been examined. We herein showed that oxLDL decreased EC-SOD mRNA and protein levels by binding to lectin-like oxidized LDL receptor-1 (LOX-1). Moreover, we demonstrated the significant role of mitogen-activated protein kinase (MEK)/extracellular-regulated protein kinase (ERK) signaling in oxLDL-elicited reductions in the expression of EC-SOD and proliferation of VSMCs. The results obtained with the FCS treatment indicate that oxLDL-elicited reductions in the expression of EC-SOD are related to the proliferation of VSMCs. We herein showed for the first time that luteolin, a natural product, restored oxLDL-induced decreases in the expression of EC-SOD and proliferation of VSMCs. Collectively, the results of the present study suggest that oxLDL accelerates the development of atherosclerosis by suppressing the expression of EC-SOD and also that luteolin has potential as a treatment for atherosclerosis. J. Cell. Biochem. 117: 2496-2505, 2016. © 2016 Wiley Periodicals, Inc.

Cross Talk Mechanism among EMT, ROS, and Histone Acetylation in Phorbol Ester-Treated Human Breast Cancer MCF-7 Cells

Epithelial-mesenchymal transition (EMT) plays a pivotal role in the progression of cancer, and some transcription factors including Slug and Snail are known to be involved in EMT processes. It has been well established that the excess production of reactive oxygen species (ROS) and epigenetics such as DNA methylation and histone modifications participate in carcinogenesis; however, the cross talk mechanism among EMT, ROS, and epigenetics remains unclear. In the present study, we demonstrated that the treatment of human breast cancer MCF-7 cells with phorbol ester (TPA), a protein kinase C activator, significantly induced cell proliferation and migration, and these were accompanied by the significant induction of Slug expression. Moreover, the TPA-elicited induction of Slug expression was regulated by histone H3 acetylation and NADPH oxidase (NOX) 2-derived ROS signaling, indicating that ROS and histone acetylation are involved in TPA-elicited EMT processes. We herein determined the cross talk mechanism among EMT, ROS, and histone acetylation, and our results provide an insight into the progression of cancer metastasis.

Clinical relevance of thyroid cell models in redox research

Background

Thyroid-derived cell models are commonly used to investigate the characteristics of thyroid cancers. It is noteworthy that each in vitro single cell model system imitates only a few characteristics of thyroid cancer depending on e.g. source of cells or oncogene used to transform the cells.

Methods

In the current work we utilized rat thyroid cancer cell models to determine their clinical relevance in redox gene studies by comparing in vitro expression data to thyroid Oncomine microarray database. To survey the cell lines we analyzed mRNA expression of genes that produce superoxide anion (nox family), genes that catalyze destruction of superoxide anion to hydrogen peroxide (sod family), and genes that remove hydrogen peroxide from cellular environment (catalase, gpx family and prdx family).

Results

Based on the current results, rat thyroid PC Cl3, PC PTC1, PC E1A, or FRLT5 cell models can be used to study NOX2, NOX4, SOD2, SOD3, CATALASE, GPX1, GPX2, GPX5, PRDX2, and PRDX3 gene expression and function.

Conclusions

Redox gene expression in rat originated single cell model systems used to study human thyroid carcinogenesis corresponds only partly with human redox gene expression, which may be caused by differences in redox gene activation stimulus. The data suggest careful estimation of the data observed in rat thyroid in vitro models.

Electronic supplementary material

The online version of this article (doi:10.1186/s12935-015-0264-3) contains supplementary material, which is available to authorized users.

Curcuminoids Modulate the PKCδ/NADPH Oxidase/Reactive Oxygen Species Signaling Pathway and Suppress Matrix Invasion during Monocyte-Macrophage Differentiation

Monocyte recruitment and invasion play critical roles in the initiation and progression of atherosclerosis. The reduction in monocyte adhesion and infiltration is thought to exert antiatherosclerotic effects. Curcumin, demethoxycurcumin (DMC), and bisdemethoxycurcumin (BDMC) are the major active components of curcuminoids and exhibit several biological activities, including anti-inflammatory, anticarcinogenic, and hypocholesterolemic activities. The aim of this study was to investigate the antiatherogenic effects and mechanisms of curcuminoids during monocyte to macrophage differentiation. The results showed that curcumin, DMC, and BDMC (20 μM) suppressed matrix invasion from 100.0 ± 5.0% to 24.8 ± 1.4%, 26.6 ± 2.9%, and 33.7 ± 1.7%, respectively, during PMA-induced THP-1 differentiation. We found that curcuminoids significantly reduced PMA-induced CD11b and MMP-9 expression by THP-1 cells. Production of reactive oxygen species (ROS) induced by PMA (126.7 ± 2.1%) was markedly attenuated by curcumin, DMC, and BDMC to 99.5 ± 7.8%, 87.8 ± 8.2%, and 89.8 ± 7.6%, respectively, resulting in the down-regulation of CD11b and MMP-9 expression. We demonstrated that curcuminoids inhibited NADPH oxidase through the down-regulation of NOX2 expression and the reduction of p47phox membrane translocation. Moreover, we found involvement of PKCδ in the PMA-induced NOX2, CD11b, and MMP-9 mRNA expression. Curcumin, DMC, and BDMC decreased the active form of PKCδ protein stimulated by PMA in THP-1 cells. Overall, our results reveal that curcuminoids suppress matrix invasion through the inhibition of the PKCδ/NADPH oxidase/ROS signaling pathway during monocyte-macrophage differentiation.

Oxidized low-density lipoprotein accelerates the destabilization of extracellular-superoxide dismutase mRNA during foam cell formation

Extracellular-superoxide dismutase (EC-SOD) is one of the main anti-oxidative enzymes that protect cells against the damaging effects of superoxide. In the present study, we investigated the regulation of EC-SOD expression during the oxidized low density lipoprotein (oxLDL)-induced foam cell formation of THP-1-derived macrophages. The uptake of oxLDL into THP-1-derived macrophages was increased and EC-SOD expression was decreased in a time-dependent manner by oxLDL. Furthermore, EC-SOD suppression by oxLDL was mediated by the binding to scavenger receptors, especially CD36, from the results with siRNA experience. EC-SOD expression is known to be regulated by histone acetylation and binding of the transcription factor Sp1/3 to the EC-SOD promoter region in human cell lines. However, oxLDL did not affect these processes. On the other hand, the stability of EC-SOD mRNA was decreased by oxLDL. Moreover, oxLDL promoted destabilization of ectopically expressed mRNA from EC-SOD or chimeric Cu,Zn-SOD gene with the sequence corresponding to 3'UTR of EC-SOD mRNA, whereas oxLDL had no effect on ectopic mRNA produced from EC-SOD gene lacking the sequence. These results suggested that oxLDL decreased the expression of EC-SOD, which, in turn, accelerated the destabilization of EC-SOD mRNA, leading to weaker protection against oxidative stress and atherosclerosis.

Curcumin binds to the pre-fibrillar aggregates of Cu/Zn superoxide dismutase (SOD1) and alters its amyloidogenic pathway resulting in reduced cytotoxicity

Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease that affects motor neurons. Unfortunately, effective therapeutics against this disease is still not available. Almost 20% of familial ALS (fALS) is suggested to be associated with pathological deposition of superoxide dismutase (SOD1). Evidences suggest that SOD1-containing pathological inclusions in ALS exhibit amyloid like properties. An effective strategy to combat ALS may be to inhibit amyloid formation of SOD1 using small molecules. In the present study, we observed the fibrillation of one of the premature forms of SOD1 (SOD1 with reduced disulfide) in the presence of curcumin. Using ThT binding assay, AFM, TEM images and FTIR, we demonstrate that curcumin inhibits the DTT-induced fibrillation of SOD1 and favors the formation of smaller and disordered aggregates of SOD1. The enhancement in curcumin fluorescence on the addition of oligomers and pre-fibrillar aggregates of SOD1 suggests binding of these species to curcumin. Docking studies indicate that putative binding site of curcumin may be the amyloidogenic regions of SOD1. Further, there is a significant increase in SOD1 mediated toxicity in the regime of pre-fibrillar and fibrillar aggregates which is not evident in curcumin containing samples. All these data suggest that curcumin reduces toxicity by binding to the amyloidogenic regions of the species on the aggregation pathway and blocking the formation of the toxic species. Nanoparticles of curcumin with higher aqueous solubility show similar aggregation control as that of curcumin bulk. This suggests a potential role for curcumin in the treatment of ALS.

Gold drug auranofin could reduce neuroinflammation by inhibiting microglia cytotoxic secretions and primed respiratory burst

Neuroinflammation contributes to the pathogenesis of neurological disorders. Anti-inflammatory treatments could potentially be used to slow down the progression of these diseases. We studied the anti-neuroinflammatory activity of gold compounds which have been used to treat rheumatoid arthritis. Non-toxic concentrations of auranofin (0.1-1 μM) significantly reduced the cytotoxic secretions by primary human microglia and microglia-like THP-1 promonocytic cells. Auranofin inhibited primed NADPH-oxidase dependent respiratory burst and secretion of tumor necrosis factor (TNF)-α and nitric oxide by monocytic cells. It had a direct neuroprotective effect on SH-SY5Y neuronal cells. Auranofin could have a novel application in the treatment of neurodegenerative diseases.

Effects of selenoprotein S on oxidative injury in human endothelial cells

Background

Selenoprotein S (SelS) is an important endoplasmic reticulum and plasma membrane-located selenoprotein implicated in inflammatory responses and insulin resistance. However, the effects of SelS on endothelial cells (ECs) have not been reported. In the present study, the role of SelS in oxidative stress and the underlying mechanism were investigated in human ECs.

Methods

A SelS over-expression plasmid (pc-SelS) and a SelS-siRNA plasmid were transfected into human umbilical vein endothelial cells (American Type Culture Collection, USA). The cells were divided into four groups: control, SelS over-expression (transfected with pc-SelS), vector control, and SelS knockdown (transfected with siRNA-SelS). After treating the cells with H₂O₂, the effects of oxidative stress and the expression of caveolin-1 (Cav-1) and protein kinase Cα (PKCα) were investigated.

Results

Following treatment with H₂O₂, over-expression of SelS significantly increased cell viability and superoxide dismutase (SOD) activity, and decreased malondialdehyde (MDA) production and Cav-1 gene and protein expression. However, no effects on PKCα were observed. In contrast, knockdown of SelS significantly decreased cell viability, SOD activity, and PKCα gene and protein expression, and increased MDA production and Cav-1 gene and protein expression.

Conclusions

SelS protects ECs from oxidative stress by inhibiting the expression of Cav-1 and PKCα.

Epigenetic regulation of extracellular-superoxide dismutase in human monocytes

Extracellular-superoxide dismutase (EC-SOD) is a major SOD isozyme mainly present in the vascular wall and plays an important role in normal redox homeostasis. We previously showed the significant reduction or induction of EC-SOD during human monocytic U937 or THP-1 cell differentiation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA), respectively; however, its cell-specific expression and regulation have not been fully elucidated. It has been reported that epigenetic factors, such as DNA methylation and histone modification, are involved in several kinds of gene regulation. In this study, we investigated the involvement of epigenetic factors in EC-SOD expression and determined high levels of DNA methylation within promoter and coding regions of EC-SOD in THP-1 cells compared to those in U937 cells. Moreover, treatment with a DNA methyltransferase inhibitor, 5-azacytidine, significantly induced the expression of EC-SOD in THP-1 cells, indicating the importance of DNA methylation in the suppression of EC-SOD expression; however, the DNA methylation status did not change during THP-1 cell differentiation induced by TPA. On the other hand, we detected histone H3 and H4 acetylation during differentiation. Further, pretreatment with histone acetyltransferase inhibitors, CPTH2 or garcinol, significantly suppressed the TPA-inducible EC-SOD expression. We also determined the epigenetic suppression of EC-SOD in peripheral blood mononuclear cells. Treatment with granulocyte macrophage colony-stimulating factor (GM-CSF)/granulocyte-CSF induced that expression. Overall, these findings provide novel evidence that cell-specific and TPA-inducible EC-SOD expression are regulated by DNA methylation and histone H3 and H4 acetylation in human monocytic cells.

Luteolin suppresses the differentiation of THP-1 cells through the Inhibition of NOX2 mRNA expression and the membrane translocation of p47phox

Luteolin (1), a natural product occurring in many vegetables and fruits, is known to have several biological activities. Cluster for differentiation (CD) families, such as CD11b, -14, and -36, are expressed during pathological processes of atherosclerosis and are used broadly as markers of monocytic differentiation into macrophages. Herein, it was investigated whether 1 and three other flavonoids [chrysin (2), apigenin (3), and tricetin (4)] blocked 12-O-tetradecanoylphorbol 13-acetate (TPA)-triggered induction of CD families, which were induced through the activation of protein kinase C (PKC), mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase (ERK), and NADPH oxidase (NOX)-derived reactive oxygen species (ROS). When compared to flavonoids 2-4, 1 blocked TPA-triggered induction of CD families and cell adherence of monocytic THP-1 cells. Luteolin completely blocked intracellular ROS generation, whereas it did not inhibit MEK/ERK phosphorylation. Moreover, pretreatment with 1 suppressed TPA-triggered induction of NOX2 and membrane translocation of p47(phox). Overall, it is revealed that 1 suppresses TPA-triggered induction of CD families by the prevention of NOX2 activation.